Field
The present disclosure generally relates to network communication, and more specifically to location detection of network devices in an indoor environment.
Background
Positioning techniques such as multilateration, triangulation, and trilateration rely on precise measurement of independent distances or angles in order to accurately determine positioning. For example, a global positioning systems (GPS) receiver uses multilateration to provide precise positioning anywhere on or near the Earth's surface where there is an unobstructed line-of-sight to four GPS satellites. In particular, GPS is designed so that each satellite shares a common clock and the design relies on precise positioning of each satellite being known with a very high degree of accuracy. The design implements a simplex communication in that each satellite does not receive a signal from a GPS receiver and instead assumes that each GPS receiver does not share a common clock with the satellites. Under this assumption, a GPS receiver acquires signals between at least four independent satellites to unambiguously distinguish a position instead of three independent satellites. In particular, the GPS receiver calculates a first difference in distance between a pair of satellite stations and calculates a second difference in distance between a different pair of two satellite stations based on broadcasts sent from the each satellite at known times.
Because GPS relies on line-of-sight signals from at least four satellites to determine positioning, a GPS receiver may not work when some of the satellite signals are obstructed. For example, a GPS receiver may not work indoor environments (e.g., inside buildings) since obstructions may attenuate satellite signals beyond the four satellites coverage. In addition, the multiple reflections at surfaces cause multi-path propagation serving for uncontrollable errors.
For indoor environments, relative signal strength indicators (RSSI) or received channel power indicator (RCPI) from stations may be used to assist in location determination. In particular, a network system may use triangulation or trilateration based on RSSI or RCPI measurements that are piggy-backed on known locations (e.g., anchor locations) from GPS measurements to provide relative locations within an indoor environment. The drawback of this technique is that RSSI and RCPI measurements are susceptible to obstructions and reflections that result in inaccurate measurements. The inability to reduce RSSI measurement error has hindered the determination of accurate location of indoor environment. As such, indoor environment location determination techniques would benefit from techniques to provide accurate coordinates from RSSI measurements despite the measurement error.